import java.util.Random;

public class test3 {
    static void main() {
        char[] chs = new char[52];
        for (int i = 0;i < chs.length;i++) {
            if (i < 25) {
            chs[i] = (char)(97+i);
            }else  {
            chs[i] = (char)(65+i-26);
            }
        }
        String result = "";
        Random r = new Random();
        for (int i = 0;i < 4;i++) {
         int  randomIndex = r.nextInt(chs.length);
        result += chs[randomIndex];}
        int number = r.nextInt(10);
        result += number;
        System.out.println(result);
    }
}
